Conventionally, an ultrasonic diagnostic apparatus is on a smaller scale than other medical imaging diagnostic apparatuses such as an X-ray diagnostic apparatus, an X-ray computed tomography (CT) apparatus, and a magnetic resonance imaging (MRI) apparatus. In addition, an ultrasonic diagnostic apparatus can display the movement of a test subject such as beating of the heart and fetal activity in real time, by a simple operation of placing an ultrasonic probe onto the surface of the body. For these reasons, the ultrasonic diagnostic apparatus plays an important role in the current medical field. Because there is no possibility of receiving radiation with the ultrasonic diagnostic apparatus, downsized apparatuses that are portable with one hand have been developed, and such ultrasonic diagnostic apparatuses can be readily used in medical practice such as obstetrics and home medical care.
Recently, as the resolution of ultrasonic images has been dramatically improved in accordance with the improvements of high-frequency probes and developments of image processing technology, the use of the ultrasonic diagnostic apparatus has been rapidly increased. For example, in the field of orthopedics, the subject of observation is soft tissue having a layered structure in which small fibers are gathered in a bundle, such as muscle and tendon, and the ultrasonic diagnostic apparatus can display this layered structure as an ultrasonic image. Thus, ultrasonic images are adopted as a useful means of clinical observation, and a doctor suspects of some abnormality if there is any loss or rupture of the layered structure observed in a ultrasonic image.
It is difficult, however, for an inexperienced person to discover such an abnormality in the ultrasonic image. In addition, if a smoothing process is performed on the ultrasonic image so as to make it easier to examine, useful clinical information may be lost. Because the examination of an ultrasonic image depends on the ability of the examiner, quantitative representation of the information displayed on the ultrasonic image has been demanded.